Unusual conformational stability of a sterically crowded atropisomer of methyl[α4-5,10,15,20-tetrakis(2′-phenylphenyl)porphyrinato]aluminium: a possibility of CH–π bonding interactions in organometallic porphyrin systems

Abstract

Through conformational studies on the topologically well-defined atropisomeric systems of organo-aluminium and -cobalt porphyrins, e.g. methyl[α⁴-5,10,15,20-tetrakis(2′-phenylphenyl)porphyrinato]aluminium (α⁴-1a), the presence of intramolecular CH–π bonding interactions are indicated between alkyl groups bonded to the central metal atoms and aromatic rings located at the ortho position of the meso phenyl substituents upon proximal orientation.